CA1198957A - Printing screen cleaning and reclaiming compositions - Google Patents
Printing screen cleaning and reclaiming compositionsInfo
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- CA1198957A CA1198957A CA000414431A CA414431A CA1198957A CA 1198957 A CA1198957 A CA 1198957A CA 000414431 A CA000414431 A CA 000414431A CA 414431 A CA414431 A CA 414431A CA 1198957 A CA1198957 A CA 1198957A
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Abstract
PRINTING SCREEN CLEANING AND
RECLAIMING COMPOSITIONS
Abstract of the Disclosure Ink cleaning compositions are disclosed which degrade or solubilize broad classes of printing ink residues on print-ing screens for quick removal by a pressurized water stream.
The compositions axe essentially non-aqueous and contain N-methyl-2-pyrrolidone, an oxygenated solvent, such as butyl cellosolve and cyclohexanone, and a surfactant. Methods of cleaning and reclaiming printing screens which provide syner-gistic activities are also disclosed. The compositions meet health and safety standards due to their biodegradability, lack of flammability and high threshold limit values.
RECLAIMING COMPOSITIONS
Abstract of the Disclosure Ink cleaning compositions are disclosed which degrade or solubilize broad classes of printing ink residues on print-ing screens for quick removal by a pressurized water stream.
The compositions axe essentially non-aqueous and contain N-methyl-2-pyrrolidone, an oxygenated solvent, such as butyl cellosolve and cyclohexanone, and a surfactant. Methods of cleaning and reclaiming printing screens which provide syner-gistic activities are also disclosed. The compositions meet health and safety standards due to their biodegradability, lack of flammability and high threshold limit values.
Description
~'3~
Related Appllcation This application is related to copending, commonly assigned Canadian application serial no~ ,440, filed October 28, 1982.
Background of the Invention Screen printin~ is a well establishecl a;ld sub-stantial industry. Essential:ly, printing screens are imparted with various desic1ns, art work or printed indicia by rather permanent emulslons on the screen ~or localized application of dye pastes or inks used in reprod~lcin~ the image from the screen. rhe emulsions surroundinc) the image areas of the printed screens are resistant to inks so that they resist removal durin~ the printing process when ink is applied through the screen for reproduction oE the ima~es there~rom. ~rhe same qualities which make emulsions resistant to ink and cleaning solvents can make them more difficult to be removed from a printed screen. ~rinting screens are usually made from silk, synthetic fabric or metal materials and, in the practice of screen printing, it is common to reuse them. This involves a cleaning process whereby ink residue from one pxinting operation will be removed and cleaned fromthe screens which permits their storage and later reuse. In the removal of ink, it is sometimes impor-tant not to affect the emulsion area which has been imparted to the screen. Modern day screen printing has evolved rather complex ink or dye formulations which are sometimes very difficult to remove. Agents which may be suitable to clean inks from the screens may also affect the underlying emulsion. Therefore, screen printing involves a balanced variety of chemical processes in which screens are prepared from artwork with semi- to fully-permanent emulsions for reproducing ink irnages in a manner such that the emulsion areas resist ink attack. In such operations, the screen is repeatedly cleaned for filinq and/or subsequent reuse. It is ' J(l~h/~ 1 also important that the screen be capable of reclamation when ink image and/or emulsion areas are removed with different types of screen reclaiming solutions or agents.
Commercial screen printing shops usually clean or reclaim many screens daily and, for this purpose, employ screen cleaning machines or reclaiming systems. Such cleaning machines or reclaiming systems usually employ recirculating solven~s which allow the synthetic or metal screens to be introduced and either cleaned or recl~;re~, depending upon production requirements. In addition, other co~nercial operations involve hand-cleaning or reclA;m;ng with various solvents or corrosive agents. During the course of cleaning or reclaiming, the screen printer is often in intimate contact with the chemicals or solvents. 'rhere are many solvents or agents used in screen cleaning and reclamation. The three most commonly used agents may be classified as aliphatic hydrocarbons, aromatic hydrocarbons and oxygenated solvents, and less fxequently, chlorinated solvents. Aliphatic hydrocarbons are commonly referred to as "mineral spirits" but more accurately these aliphatic solvents are composed of mixtures of straight-chain and/or branched-chain saturated hydrocarbons. The higher tha molecular weight or the number of carbon atoms, the higher the boiling point of the solvent~ The higher the boiling point, the slower the solvent will evaporate, hence, usually the higher boiling aliphatic hydrocarbons are desirable for use in screen cleaning The aromatic hydrocarbon solvents include cyclic hydrocarbons containing th~ benzene ring. These aromatic hydrocarbons are usually more flAm~hle but much stronger in solvation power ' than the aliphatic type solvents and, similarlyt the higher the molecular weight for the aromatic hydrocarbon, the higher the boiling range. In contrast to the rather non-polar hydrocarbons, oxygenated solvents are more polar compounds.
Typically, o~ygenated solvents are those having hydroxyl or carbonyl groups, and many of them have considerable solubility in water. Other solvents include chlorinated solvents which are fully- or semi-chlorinated hydrocarbons and the rarely used fluorlnated hydrocarbons of the ~reon types.
Today's screen printer thus routinely deals with a multiplicity of solvents which are used ~or screen cleaning and reclamation. In the past r when there was perhaps li~tle understanding of the health and safety hazards which printers or workers were exposed to, such solvents were used with impunity. More recently, in view of Federal and State legis-lation, solvents must meet material safety standards. Pro-longed or repeated solvent contact with the skin is ger,erally avoided and, in most instances, because of flammability, solvents must be kept away from e~LLe.,e heat or open flame, and frequently fire departments request their storage outside.
Occupational Safety and Health A~m; n; strations at both Federal and State lavels have also placed various restrietions upon ths use of solvents and, many may no longer be used. Furthermore, in known processes, hot reclamation systems have been required in order to clean or reclaim printing screens, but such systems create pollution and hazards which are no longer tolerable. In the search for suitable screen cleaning and reclamation 501-vents or agents, it would ~e desirable to be able to eliminate the DOT (Department of Transportation) red label which warns of hazardous, fl~mm~hle solvents. It would also be desirable to j, offer cle~n;ng and reclamation compositions which are either , /
C
I, ~0' completely or essentially biodegradable. Another highly desirable objective would be to make available to the industry cleaning and reclamation products having a high threshold limit values (TLV) which means that the amount of airborne matter provided by such products offers greater safety in breathing.
The above background provides a practical overview of the screen printi~g industry from the standpoint of the cleaning and reclamation processes to a person of ordinary skill in this art. In addition, in the preparation of this application, patents have been located which may be considered to relate to the subject matter of this invention. The following is a list of prior patents which may be helpful in understanding this invention without leaving the impression that it is exhaustive or that there may not be more relevant patent art or litexature: U.S. Patent Nos. 2,780,168;
3,459,594; 3,511,657; 3,615,827, 3,642,537; 3,673,099;
3,679,479, 3,706,691; 3,737,386; 3,764,384; 3,789,007;
3,796,602; 3,928,065; 3,953,352, 4,024,085; 4,055,515 and 4,070,203. It must be mentioned that these patents have been listed with the knowledge of this invention and even have been obtained from non-analogous arts. Therefore, it is not to be in any way inferred that their lis~ing here represents the state of the printing screen cleaning or reclamation art.
It is submitted that there is a need for printing screen cleaning and reclamation compositions which are effec-tive in a wide variety of applications. Moreover, it is highly desirable that such compositions, while effective, neverthe-; less, meet environmental health and safety standards.
3~7 Summary of the Invention This invention is directed to printing screen cleaning or reclaiming compositions which are generally effective in solva~ing or degrading inks used in the printing industry. The ink cleaning composikions not only solubilize or degrade broad classes of prin~ing inks, but also possess high or no flash points, excellen~ biodegradabili~ies and high threshold limit values. Thus, the health and safety of the screen printer or worker in the industry is exceedingly enhanced by this invention. In addition, this invention provides for a system of cleaning and reclA;m;ng compositions which are synergisticaLly operative whereby inks can be ~ oved and the printed emulsion on the screen may be sensitized for effective removal. In addition, in another of its general aspec~s, this invention involves a mekhod or cleaning or cleaning and rect~im;~g printing screens made of silk, textile, metal or other types, without damaging the screen and to place it in an immediate condition for either storage or reuse.
The unique compositions of this invention consist essentially of N-methyl-2-pyrrolidone (herein simply sometimes "NMP"), an oxygenated solvent and a suxfactant. It has been found that a non-aqueous system of these essenkial components will soIubilize or degrade a wide variety of polymeric or other inks currently being employed in the modexn screen p~inting industry. This composition has been found to penet~ate, emulsify and prevent redeposition of inks during ~heir Le.,loval from a variety of common printing screens, It has also been discovered that the NMP, oxygenated solvent and surfac~ank composition must be non-aqueous in order to effectively clean :. ~
screens or to sensitize the ink-free screen Eor subsequent emulsion removal, if desired.
In other aspects, a screen c]eanin(1 or reclama-tion process is provided by applying the non-aqueous NMP, oxygellated solvent ancl s~ factant systelll (hert?in sometlmes simply "NMI' concentrate") onto a screen surEace for a suEEicient dwell time to enab:Le solubilization or degradation o~ thc ink. Then, the ink may be rinsed with water to remove it from the screen. By this method, the ink is degraded to a point whereby a meAium to high pressure, low-volume water spray will permit the complete removal of ink. A5 also disclosed and claimed in copending application serial no. 4l4,440, a preerred method for applying the N~IP conGentrate is to spray it onto the screen :ink surface.
Spraying a coherent spray oE the NM~ concentrate enables extremely low amounts to be used and degradation may still surprisingly be achieved. It has also been found that, after tlle ink cleaning step with the NMP concentrate, the emulsion is in a sensitized state for removal Erom the screen with a periodate-containing emulsion remover. The screen may thus be totally reclaimed. Thereafter, if further desired, any image ink residue or "ghost" as the term is used in the trade, may be removed with a caustic solution containing oxygenated solvent. By the above seguence, this invention also provides for an overall screen cleaning and reclamation process.
As developed in the background of this inven-tion, hot solvent and alkaline techniques have been employed in the prior art screen cleaning and reclamation. This invention avoids the need for such ho-t cleaning techniques and the associated health mab/
hazards created by such techniques. In ano~her of its aspects, the invention is capable of performance at ambient or roo~
temperature conditions. In this essential respect, it is considered highly unexpected and unobvious that a cleaning and reclamation process could operate at such low or ambient temperatures and be as effective in removing a wide variety of ink compositions. Furthermore, whereas it has been disclosed in prior patents to employ derivatives of pyrrolidone including alkyl pyrrolidones, in cleaning compositions, it has not heretofore been suggested that any such pyrrolidone derivative may be employed in a composition for the removal o screen printing ink compositions. Furthermoxe, even where pyrxolidones have been sugges~ed in non-analogous art , they generally are employed in aqueous systems in contrast to the essentially non-aqueous concentrates of this invention. Also, for purposes of this invention, N~methyl-2-pyrrolidone is essentially required to operate in combination with oxygena~ed solvents and surfactants in order to achieve the most optimum desired results. In substance, in the screen prlnting industry, it has not be~n heretofore suggested that a non-toxic, biodegradable and very safe cleaning composition may be provided, and still achieve highly desirable cleaning and synergistic reclamation effects t as has been provided by the compositions of this invention.
l~ '.'' ~
5'7 i Detailed Description of the Invention As delineated above, the essential components of the inventive compositions are N-methyl-2-pyrrolidone, an oxy-genated solvent and a suractant. In a preferred composition, the oxygenated solvents are a combination of butyl cellosolve and cyclohexanone. These pxeferred oxygenated solvents are from the class of glycol ethers, alcohols and ketones, respectively. Other classes o applicable oxygenated solvents include esters and ethers, and mixed classes thereof. The surfactant is preferably from the group consisting of nonionic or anionic surfactants, or mixtures thereof, and a specific example of nonionic surfactant is octyl phenoxy (polyethoxy) ethanol of Rohm & ~aas, sold under the trademark TRITON X-114 and an organic phosphate ester sold under the trademark GAEAC
RP-710 by General Analine and Film Corpoxation. Further examples of oxygenated solvents from tlle class of glycol ethers which may be used include methyl cellosolve, hexyl cellosolve, cellosolve solvent, methyl carbitol r carbitol solvent, butyl carbitol, hexyl carbitol, and the like. Other examples of ketones include methyl ethyl ketone, methyl isobutyl ketone, methyl isoamyl ketone, ethyl butyl ketone, isobutyl heptyl ketone, isophorone, diacetone alcohol, acetone, 4-methoxy-4-methyl-2-pentanone, and the like. Other examples of ethers include butyrolactone, diethyl carbitol and dibutyl carbitol, and others. Examples of esters include butyl lactate, butyl acetate, butyl carbitol acetate, carbitol aceta~e, butyl cellosolve acetate, cellosolve acetate, 2-ethyl hexyl acetate, amyl acetate, methyl cellosolve acetate, formates, and others.
Bxamples of alcohols include amyl alcohol, bu~yl alcohol, 5'~
furfurol alcohol, 2=butyne-1,4,diol, tetrahydrofurfurol alcohol, and others. Therefore, in accordance with the broader principles of this invention, oxygenated solvents from the above mentioned classes are suitable for use, depending upon the required solvating capacities of the oxygenated solvents in order to obtain the most desired biodegradability, least flammability and highest threshold limit values to meet or exceed health and safety standards. In accordance with the preferred principles of this invention, however, as mentioned above, there are specific examples which meet all of these criteria in the most preferred aspects of this invention~ In a generic aspect, the oxygenated solvent acilitates the low viscosity solvating character of the NMP and helps disperse it to solubilize or degrade the ink compositions. The NMP is also water active when needed. Thus, the combination of the NMP and the oxygenated solvent provide a coaction between organic co-solvents along with a unique water activity to provide a synergistic action in solvating or degrading ink compositions on screens for removal with water. Yet, it is imperative that the NMP concentrates be essentially non-aqueous during solvation or degradation o~ ink becau~e any significant water will destroy the efectiveness of NMP in its cleaning power as it is used in this invention. ~owever, the solvated or degraded ink must then be in a state for removal with a low-volume, pressurized stream of water.
In addition to the surfactants mentioned above, other nonionic, anionic, cationic and amphoteric surfactants may be used, as listed primarily in McCutcheon's Detergents and Emulsifiers, 1980 Edition, MC Publishing Company, Glenrock, New Jersey. The surfactants aid in the dispersion and degradation ~9~J~'7 !
of the inks for aqueous removal. Surfactants of the anionic type may be (1) of the group of saponified fatty acids or ~oaps, or (2) of saponified petroleum oil such as sodium salts or organic sulfonates or sulfates or (3) of saponified esters, alcohols or glycols, with the latter being well known as anionic synthetic surfactants. Examples of these anionic surfactants include the alkaryl sulfonates or amine salts thereof such as sulfonates of dodecyl benæene or diethanolamine salt of dodecyl benzene sulfonic acid. Most of these sulfonates contain many chemical species. The clas~ name given to most of them is ~alkylaryl sulfonate". Simply, this means that a paraffinic hydrocarbon is bonded to an aromatic or b~nzene nucleus and the aromatic portion has been sulfonated.
Examples of saponified fatty acids (C6-C2~) are the sodium or potassium salts of myristic, palmitic, s~earic, oleic or linol~ic acids or mi~tures thereof. Also in this class of anionic surfactants are organic phosphate esters including ~lk~li and alkaline earth metal salts of neutral phosphoric acid esters of oxylalkylated higher alkyl phenols or aliphatic O monohydric alcohols. Aerosol OT iS a dioctyl alkali metal sulosuccinate anionic surfactant made by Cyanamide. The nonionic surfactants suitable for use commonly have hydrophylic portions or side chains usually of the polyoxyalkylene type.
The oil soluble or dispersible part of the molecule is derived rom either fatty acids, alcohols, amides or amines. By suitable choice of starting materials and regulation of the length of the polyoxyalkylene chain, the surfactant parts of the nonionic detergents may be varied as is well known.
Suitable examples of no~ionic surfactants include alkylphenoxy , polyoxyethylene glycol, ~or example, ethylene oxide adduct of j .
*trade mark either octyl-, nonyl- or tridecyl- phenol and the like. These mentioned nonionic surfactants are usually prepared by the reaction of the alkyl phenol with ethylene oxlde. Commercial products are sold under the trademarks "Triton X-100 or X-114"
by Rohm and Haas Co. or "Tergitol" by Union Carbide and Carbon Corp. which are alkyl phenyl ethers of polyethylene glycol.
Other specific examples of nonionic surfactants include glyceryl monooleate, oleyl monisopropanolamide sorbitol di-oleate, alkylol amides prepared by reacting alkanolamides such as monoisopropanolamine, diethanolamine, or monobutanol ~m; ne with fatty acids such as oleic, pelargonic, lauric and the like. The cationic surfactants are also well developed and mainly include betaines and quaternary ammonium compounds.
Some specific examples of betaine~ include imidazoline hataines, aliphatic and carboxcyclic betaines, and betaines with hetero atoms in the hy~o~hobic chains such as dodecyloxypropyldimethyl aminoacetic acid. Typical of the quaternary ammonium compounds that may be mentioned are dime~hyl dicoco ammonium chloride, cetyl pyridinium acetate, methyl cetyl piperidinium proprionate, N,N dilauryl, N,N
dimethyl ammonium diethophosphate, and the like. Thu , i~ will be understood that o~her anionic~ cationic, amphoteric or nonionic surfactants may be employed in accordance with the principles of this inven~ion.
The amounts o ingredients vary over wide ranges, however, it is preferred to use a significant amoun~ of ~he N-methyl-2-pyrrolidone, iOe., about 30-85% by weiyhtO The oxygenated solvent is usually contained in an amount of about 15-35~ by weight. The remainder o the composition comprises a surfactant or a mix~ure of surfactants within the range of about 1 to about 5~ by weight. The N~ concentrates may also be supplemented with o~her organic solvents such as methylene chloride, trichloroethane, dimethyl sulfoxide and its deriva-tives t fluorocarbons and freons in amounts of about 10-30~ by weight where additional faster penetxating power may be desired for better ink solubili~ation. Such organic solvents are permitted which would not alter the essential cha~acteristics of the i~k cleaning compositions of this invention and may help to enhance activity penetration of the co-solvents in pene-trating, emulsifying and accelerating the degradation of the inks for subsequent removal.
In order to further illustrate the invention, refer-ence is made to the specific operating formulas detailed hereinafter and detailed methods of cleaning and reclaiming a printing screen.
EX~MPLE 1 75.72~ N-methyl-2-pyrrolidone 18.52~ Butyl Cellosolve 3.04% Cyclohexanone 2062% Octyl Phenoxy (Polyethoxy) Ethanol (TRITON-X-114) 0~10~ Organic Phosphate Ester (GAFAC RP-710) l2 ., 37.86~ N-methyl-2-pyrrolidone 9.26% Butyl Cellosolve 1.52~ Cyclohexanone 24.00~ Cellosolve Acetate 26.00~ Methylene Chloride 1.31~ Octyl Phenoxy (Polyethoxy) Ethanol (TRITON X114) 0.05% Oryanic Phosphate Ester (GAFAC RP-710) In the alternative to the specific ingredients of Example 2, 50% of Example 1 may be combined with ~6% of methy-lene chloride and 24~ cellosolve acetate. Examples 1 and 2 are preferxed forr~ s for the NMP cleaning concentrates because of their hiodegradability, reduced flammability and low TLV
values.
Before describing in detail the cleaning and re-cl~; ing of printing screens emloying the compositions of this invention, an understanding of certain underlying facts or terms is important. Flrst of all, the ink side o the printing screen is altPrnately called the squeegee side, the well side, or the front side, but or purposes of ~his description it will be called the ink side. The opposite side of the screen is called the back side, down side or prin~-contact side~ Again, for purposes of this description, it will be called the print~
contact side. The term "ink" will be ~he generic term for many I of the compositions that are employed in the practice of screen , printing including dyes or inks c~ ~-ly refPrred to as flexible enamels, synthetic enamels, fast-dry enamels, flexible lacquers, industrial lacquers, fla~ vinyl ink, vinyl half-tone . l3 :~4-~ 7 ink, fluorescent vinyl ink, gloss vinyl ink, satin vinyl ink, flock adhesive, transparent ink, metallic powders, acrylic ink, plastisol ink, mylar ink, ~extile ink, among many other types of inks. For general information on ink compositions, reference may ~e had to the catalog by KC Graphics, Inc.
1978-1979, copyright 1978 by KC Graphics, Inc. Reference may also be had to "Textile Screen Printing" by Albert Koslof~, Second Edition, International S~andard Book Number 0-911380-39-6 (1976). These sources will also serve as background information for the inks which may be cleaned with the inventive cleaning compositions. As developed above, the printing screen may be made from a number of materials and may have various mesh sizes. A mono-filament screen is a single strand of material for example of polyestex, nylon, stainless steel, silk, chrome-plated wire, or other things, which is woven into a specific number of squares per a ~ nsion~ i.eO, a 230 mesh means 230 open squares per square inch. A
multi-f;lAm~nt screen is comprised of a series of strands of similar materials jus~ mentioned, braided before weaving into the mesh measurement, i.e., 12xx150 mesh-would mean 12 interwoven strands subsequently woven into 150 open squares per square inch and, where th~P cross-over points of mesh occur, pigment can get into the strands and may become extremely hard to L~ ve. Thus, it may be determined by this description of I either the mono-filament or the multi-f;l~Qnt screens that the i requirements for complete removal of ink residue, for instance, may differ due to the construction of the screen. In particular, that last residue often referred to in the art as "ghost" ar "haze" would be more readily apparent in the ! multi-filament screens where pigment can get into ~he strands and becomes very hard to remove. There are a number of classes of emulsions which initially cover the print-contact side of the screen. For instance, a direct emulsion is a water-reducible substance which cures to a temporary, non-removable substànce when exposed to specific wavelengths light~ For instance, the art work can be placed over the fresh emulsion while it is still reactive to water and exposed to halide light, at which time the part o the emulsion not exposed to the light, because it is covered with the art, stays water-reactive. After a certain shooting or light exposure time, the art is Le...oved, the screen is then flushed with water and the part that has not been exposad to the light is flushed ou~, leaving the emulsion-void image area through which the ink flows through the screen for printing. The measure of difficulty of emulsion removal also relates ~o the number of coats which are put on the mesh, that is, dried and reapplied, and so forth, until you have between, for instance, 2 to about 5 coats of emulsion. Thus, the degree of difficulty in removing emulsion depends upon a number of factors including the number of coats, whethex it i5 strongly sensitized, the exposure time, type of light activation and chemical hardeners used after emulsion development, among other factors.
In view of the above b~ckground, the cleaning composition of Example 1 is a liquid non-aqueous solvent ! concentrate having a flash point of approxima~ely 203F ~95C) and it is designed to remove a large variety of inks and paints from screens. In another feature of the inven~ion, NMP
concentrate of Example 1 prepares or sensitizes many common ` emulsions for subsequent removal with a low-volume, high pressure water rinsing. It is fast, efficient, economical by . 15_ its capability of low-volume usage, biodegradable and does not carry the red label ~DOT flammable~ solvent designation. It is also safe on all screens and can be left on screens for extended periods prior to rinsing for cleaning. The composltion of Example 1 may be employed in a recirculating solvent system or in other portable systems. In the case of a recirculating solvent system, Example 1 concentrate is allowed to flow on the ink side of an inclined screen, whereupon it may be drained for approximately 5 minutes. Alternatively, the ink side of the screen may be sprayed in a light even pattern with a cohesive spray to prevent volatilization, followed by a dwell time of about 2-5 minutes. A pressurized unit is operated for example under about 30 to 100 psi (normally 40 psi) to provide a coherent stream of concentrate from a nozzle about 6" to 12"
away from the screen. Mists are avoided. In the case of either the recirculating solvent or spray treatment, the degraded inks are then easily removed by a light to high pressure, i.e., approximately 50 to 1000 psi, low-volume water rinse. Low-volume means 2 - ~ gallons per minute. A fan spray ~o has been found preferred to provide a balance of force and quantity. A suitable fan spray nozzle is the UniJet 65/01 manufactured by Spraying Systems Company of Wheaton, Illinois.
It is importan~, as developed above, that the screens on which the ink will be solubilized or degraded are free from water prior to cleaning. The presence of wa~er either in the NMP
concentrate or on the screen greatly destroys the efectiveness of the composition.
It has been found that the most preferred cleaning technique for achieving the advantages of the invention is the 3~ , method disclosed and claimed in said application Serial No.
"
*trade rnark by Cord and Valasek. In said application, the cleaning concen-trate is sprayed onto the ink side of the screen in a light even pattern and allowed to dwell or a short period of time, i.e., several minutes up to several hours, depending upon the factors involved in the cleaning system, composition of the inks, production timing, and so forth. During the dwell time, the liquid cleaning concentrate penetrates, emulsifies and solubilizes the inkO The ink stays on the screen, but its former ink character is destroyed. During the dwell time, the co-solvent actions of N-methyl-2-pyrrolidone and the oxygenated solvent are at work. Furthermore, the surfactant is pene-trating the ink composition for dispersion and to aid in later ink removal by water. The coaction of all three ingredients permits the solubili~ation or degradation of the ink permitting it to be dispersed for removal. The N-methyl-2-pyrrolidone provides water activity to the composition for removal with water, however, water must be under pressurized conditions such that the ink composition may be blown out; i.e., blown away from the screen. Thus, the composition is a delicate b~l~nce of ingredients whereby organic componen~s of the ink may ~e solubilized or degraded by both the N-methyl-2-pyrrolidone and oxygenated solvents. Fur~herr~rer even though water during the presence of the solubilization and degradation of the ink would i be detrimental to the activity of N-me~hyl-2~pyrrolidone, nevertheless, the degraded ink in the presence of the NMP and cosolvent is water-active and may be Lemo~ed from the screen with a pressurized fan of low-volume water rinse. In this connection it is preferred to employ a slicing fan or stream of water and sweeping it across the screen from the bottom upwards -in a manner such that the ink may be removed without redeposi-tion.
The composition of Example 2 above is employed in the same manner for cleaning as ~he liquid solvent concentrate of Example 1. However, the presence of methylene chloride tends to enhance the penetration o~ the entire composition and cellosolve acetate enhances the water solubility of ~.he composition. Other organic solvents which may be substituted for the methylene chloride include other chlorinated solvents like l,l,l-trichloroethane, dimethyl sulfoxide, its derivatives and fluorocarbons or Freons. In either case, the addition of such an organic ~olven~ which enhances penetration, may also tend to evaporate and, therefore, has a much shorter wet life or dwell time on the screen. For instance, whereas the composition of Claim 1 may be left on the screen surface for a number of hours, the composition of Example 2 is usually employed or several minutes, i.e., between 2-5 minutes for example. It is to be furthex understood that the ink solubilizer of Example 1 may be sequentially used in combination with the cleaning concentrate of Example 2. For instance, during the course of a cleaning operation, the ink may be solubilized with the Example 1 concentrate where an operation may require screens to be left from production for a period of time up to several hours prior to the rinse removal of the ink. In such a case~ the dwell tlme may be followed by a fresh degrading concentrate of Example 2 so that the residue i may be activated for subsequent removal with a low-volume, high pressure water rinse. Furthermore, the amounts of the mate rials sprayed onto the substrate vary but normally they are ,, ~., '.. ; /~
!;
t7 within the range of several ounces per several square feet, for example, 2-4 ounces per 6 foot square of screen.
Thus, preferably the method involves spraying of the concentrates of either of the Examples 1-2 onto a scraen. The spray is an economical and low volume usage ~ollowed by dwell time to solubilize or degrade the ink. Thereafter, a low-volume, high pressure water stream is directed at the sub strate, preferably a fan-spray is employed to slice through and help remove the destroyed ink composition. I the solubiliæed and degraded screen were simply dipped in water, the screen would not be effectively cleaned. There is a balance between the force and the quantity of the water which is employed which will be understood by the person of ordinary skill in the art in view of this description.
It has been o~served in connection wikh the method of cleaning the screens with a low area coverage spray, that a light mist may tend to settle on other rPm~; ni ng areas of degraded inks. It has been found that this problem can be alleviated or overcome by the addition of another component into the concèntrate. That component may b~ characterized as a hydrophobic additive and in particular it has been found that synthetic-water soluble oiIs sold under the tr~e~rk UCON are satisfactory. Depending upon the amount of wa~er mist or back-lash that is to be expected from the water rinse out, part of the surfactant package or liquid NMP concentrate may contain a water dispersible oil which functions ;nlti~lly as a water repellant to a light water spray or mist, but readily allows a low volume, pressurized stream of water to remove the ink ' compositions previously degraded and solubilized by the NMP
concentrate. Such water soluble oils are of the class of / q .
!
5'7 polyalkylene glycols, commonly known as UCON lubricants manufactured by Union Carbide Corporation, but other types and mixtures thereof could be used of differing water solubility.
A preferred high molecular weight one is UCON 50-HB5100.
Specific compounds include polyalkylene glycols, i.e., an oxirane polymer, CAS Registration No. 9038~95-3 or ethoxylated lanolin or exthoxylated castor oil. However, it is preferred that the oils of the types described herein do not leave a residue on the screen after an adequate water rinse.
When the printing screen is to be totally recl~im~, that is, cleaned and the emulsion removed completely, the process is as follows. When the process of printing is com-pleted, the operator cards or squeegees off any residual ink that is on the ink side of the screen as well as any ink from the print-contact side. From a very practical standpoint, inks are expensive and an attempt is made to return as much of the ink as possible. From a standpoint of cleaning, more excess ink requires more cleaning concentrate in order to remove the ink and reclaim the screen without haze or ghost residue.
After the screen is well carded, either before or after L~.. oval from the cleaning process begins. If the process is to be an i .d;ate reclaLm, either the concentrate of ~ le 1 or 2 may be used, generally spe~k;ng, depending on ink type. Either concen~rate is sprayed on the ink side of the screen and then moved to the reclaim area. In the process of immediate recla;m;ng, within about 5-10 minutes ater the application of either of the compositions of Examples 1 or 2, ;mmP~iate rec1a;r;ng should be commenced. After spraying with either concentrate, the image is flushed out from the print-con~ac~
side of the screen with high pressure water, as developed above, and this clears all o~ practically all of the ink. At the same -time, the entire surface of the emulsion is wetted with water to prepare it for the application O F a periodate-containing emulsion remover. I~ has been found that there is a synergistic action resulting rom use of the non-aqueous concentrate of ~xample 1 or 2 whose residue remains even after the water spray such that the emulsion is sensitized for faster removal. It is theorized, however, ~hat in -the immediate reclaim process, ~he emulsion is somehow softened or made more permeable for the treatment with a periodate-containing emulsion remover. A suitable example of an emulsion remover is exemplified by Example 3.
94.096% Water
Related Appllcation This application is related to copending, commonly assigned Canadian application serial no~ ,440, filed October 28, 1982.
Background of the Invention Screen printin~ is a well establishecl a;ld sub-stantial industry. Essential:ly, printing screens are imparted with various desic1ns, art work or printed indicia by rather permanent emulslons on the screen ~or localized application of dye pastes or inks used in reprod~lcin~ the image from the screen. rhe emulsions surroundinc) the image areas of the printed screens are resistant to inks so that they resist removal durin~ the printing process when ink is applied through the screen for reproduction oE the ima~es there~rom. ~rhe same qualities which make emulsions resistant to ink and cleaning solvents can make them more difficult to be removed from a printed screen. ~rinting screens are usually made from silk, synthetic fabric or metal materials and, in the practice of screen printing, it is common to reuse them. This involves a cleaning process whereby ink residue from one pxinting operation will be removed and cleaned fromthe screens which permits their storage and later reuse. In the removal of ink, it is sometimes impor-tant not to affect the emulsion area which has been imparted to the screen. Modern day screen printing has evolved rather complex ink or dye formulations which are sometimes very difficult to remove. Agents which may be suitable to clean inks from the screens may also affect the underlying emulsion. Therefore, screen printing involves a balanced variety of chemical processes in which screens are prepared from artwork with semi- to fully-permanent emulsions for reproducing ink irnages in a manner such that the emulsion areas resist ink attack. In such operations, the screen is repeatedly cleaned for filinq and/or subsequent reuse. It is ' J(l~h/~ 1 also important that the screen be capable of reclamation when ink image and/or emulsion areas are removed with different types of screen reclaiming solutions or agents.
Commercial screen printing shops usually clean or reclaim many screens daily and, for this purpose, employ screen cleaning machines or reclaiming systems. Such cleaning machines or reclaiming systems usually employ recirculating solven~s which allow the synthetic or metal screens to be introduced and either cleaned or recl~;re~, depending upon production requirements. In addition, other co~nercial operations involve hand-cleaning or reclA;m;ng with various solvents or corrosive agents. During the course of cleaning or reclaiming, the screen printer is often in intimate contact with the chemicals or solvents. 'rhere are many solvents or agents used in screen cleaning and reclamation. The three most commonly used agents may be classified as aliphatic hydrocarbons, aromatic hydrocarbons and oxygenated solvents, and less fxequently, chlorinated solvents. Aliphatic hydrocarbons are commonly referred to as "mineral spirits" but more accurately these aliphatic solvents are composed of mixtures of straight-chain and/or branched-chain saturated hydrocarbons. The higher tha molecular weight or the number of carbon atoms, the higher the boiling point of the solvent~ The higher the boiling point, the slower the solvent will evaporate, hence, usually the higher boiling aliphatic hydrocarbons are desirable for use in screen cleaning The aromatic hydrocarbon solvents include cyclic hydrocarbons containing th~ benzene ring. These aromatic hydrocarbons are usually more flAm~hle but much stronger in solvation power ' than the aliphatic type solvents and, similarlyt the higher the molecular weight for the aromatic hydrocarbon, the higher the boiling range. In contrast to the rather non-polar hydrocarbons, oxygenated solvents are more polar compounds.
Typically, o~ygenated solvents are those having hydroxyl or carbonyl groups, and many of them have considerable solubility in water. Other solvents include chlorinated solvents which are fully- or semi-chlorinated hydrocarbons and the rarely used fluorlnated hydrocarbons of the ~reon types.
Today's screen printer thus routinely deals with a multiplicity of solvents which are used ~or screen cleaning and reclamation. In the past r when there was perhaps li~tle understanding of the health and safety hazards which printers or workers were exposed to, such solvents were used with impunity. More recently, in view of Federal and State legis-lation, solvents must meet material safety standards. Pro-longed or repeated solvent contact with the skin is ger,erally avoided and, in most instances, because of flammability, solvents must be kept away from e~LLe.,e heat or open flame, and frequently fire departments request their storage outside.
Occupational Safety and Health A~m; n; strations at both Federal and State lavels have also placed various restrietions upon ths use of solvents and, many may no longer be used. Furthermore, in known processes, hot reclamation systems have been required in order to clean or reclaim printing screens, but such systems create pollution and hazards which are no longer tolerable. In the search for suitable screen cleaning and reclamation 501-vents or agents, it would ~e desirable to be able to eliminate the DOT (Department of Transportation) red label which warns of hazardous, fl~mm~hle solvents. It would also be desirable to j, offer cle~n;ng and reclamation compositions which are either , /
C
I, ~0' completely or essentially biodegradable. Another highly desirable objective would be to make available to the industry cleaning and reclamation products having a high threshold limit values (TLV) which means that the amount of airborne matter provided by such products offers greater safety in breathing.
The above background provides a practical overview of the screen printi~g industry from the standpoint of the cleaning and reclamation processes to a person of ordinary skill in this art. In addition, in the preparation of this application, patents have been located which may be considered to relate to the subject matter of this invention. The following is a list of prior patents which may be helpful in understanding this invention without leaving the impression that it is exhaustive or that there may not be more relevant patent art or litexature: U.S. Patent Nos. 2,780,168;
3,459,594; 3,511,657; 3,615,827, 3,642,537; 3,673,099;
3,679,479, 3,706,691; 3,737,386; 3,764,384; 3,789,007;
3,796,602; 3,928,065; 3,953,352, 4,024,085; 4,055,515 and 4,070,203. It must be mentioned that these patents have been listed with the knowledge of this invention and even have been obtained from non-analogous arts. Therefore, it is not to be in any way inferred that their lis~ing here represents the state of the printing screen cleaning or reclamation art.
It is submitted that there is a need for printing screen cleaning and reclamation compositions which are effec-tive in a wide variety of applications. Moreover, it is highly desirable that such compositions, while effective, neverthe-; less, meet environmental health and safety standards.
3~7 Summary of the Invention This invention is directed to printing screen cleaning or reclaiming compositions which are generally effective in solva~ing or degrading inks used in the printing industry. The ink cleaning composikions not only solubilize or degrade broad classes of prin~ing inks, but also possess high or no flash points, excellen~ biodegradabili~ies and high threshold limit values. Thus, the health and safety of the screen printer or worker in the industry is exceedingly enhanced by this invention. In addition, this invention provides for a system of cleaning and reclA;m;ng compositions which are synergisticaLly operative whereby inks can be ~ oved and the printed emulsion on the screen may be sensitized for effective removal. In addition, in another of its general aspec~s, this invention involves a mekhod or cleaning or cleaning and rect~im;~g printing screens made of silk, textile, metal or other types, without damaging the screen and to place it in an immediate condition for either storage or reuse.
The unique compositions of this invention consist essentially of N-methyl-2-pyrrolidone (herein simply sometimes "NMP"), an oxygenated solvent and a suxfactant. It has been found that a non-aqueous system of these essenkial components will soIubilize or degrade a wide variety of polymeric or other inks currently being employed in the modexn screen p~inting industry. This composition has been found to penet~ate, emulsify and prevent redeposition of inks during ~heir Le.,loval from a variety of common printing screens, It has also been discovered that the NMP, oxygenated solvent and surfac~ank composition must be non-aqueous in order to effectively clean :. ~
screens or to sensitize the ink-free screen Eor subsequent emulsion removal, if desired.
In other aspects, a screen c]eanin(1 or reclama-tion process is provided by applying the non-aqueous NMP, oxygellated solvent ancl s~ factant systelll (hert?in sometlmes simply "NMI' concentrate") onto a screen surEace for a suEEicient dwell time to enab:Le solubilization or degradation o~ thc ink. Then, the ink may be rinsed with water to remove it from the screen. By this method, the ink is degraded to a point whereby a meAium to high pressure, low-volume water spray will permit the complete removal of ink. A5 also disclosed and claimed in copending application serial no. 4l4,440, a preerred method for applying the N~IP conGentrate is to spray it onto the screen :ink surface.
Spraying a coherent spray oE the NM~ concentrate enables extremely low amounts to be used and degradation may still surprisingly be achieved. It has also been found that, after tlle ink cleaning step with the NMP concentrate, the emulsion is in a sensitized state for removal Erom the screen with a periodate-containing emulsion remover. The screen may thus be totally reclaimed. Thereafter, if further desired, any image ink residue or "ghost" as the term is used in the trade, may be removed with a caustic solution containing oxygenated solvent. By the above seguence, this invention also provides for an overall screen cleaning and reclamation process.
As developed in the background of this inven-tion, hot solvent and alkaline techniques have been employed in the prior art screen cleaning and reclamation. This invention avoids the need for such ho-t cleaning techniques and the associated health mab/
hazards created by such techniques. In ano~her of its aspects, the invention is capable of performance at ambient or roo~
temperature conditions. In this essential respect, it is considered highly unexpected and unobvious that a cleaning and reclamation process could operate at such low or ambient temperatures and be as effective in removing a wide variety of ink compositions. Furthermore, whereas it has been disclosed in prior patents to employ derivatives of pyrrolidone including alkyl pyrrolidones, in cleaning compositions, it has not heretofore been suggested that any such pyrrolidone derivative may be employed in a composition for the removal o screen printing ink compositions. Furthermoxe, even where pyrxolidones have been sugges~ed in non-analogous art , they generally are employed in aqueous systems in contrast to the essentially non-aqueous concentrates of this invention. Also, for purposes of this invention, N~methyl-2-pyrrolidone is essentially required to operate in combination with oxygena~ed solvents and surfactants in order to achieve the most optimum desired results. In substance, in the screen prlnting industry, it has not be~n heretofore suggested that a non-toxic, biodegradable and very safe cleaning composition may be provided, and still achieve highly desirable cleaning and synergistic reclamation effects t as has been provided by the compositions of this invention.
l~ '.'' ~
5'7 i Detailed Description of the Invention As delineated above, the essential components of the inventive compositions are N-methyl-2-pyrrolidone, an oxy-genated solvent and a suractant. In a preferred composition, the oxygenated solvents are a combination of butyl cellosolve and cyclohexanone. These pxeferred oxygenated solvents are from the class of glycol ethers, alcohols and ketones, respectively. Other classes o applicable oxygenated solvents include esters and ethers, and mixed classes thereof. The surfactant is preferably from the group consisting of nonionic or anionic surfactants, or mixtures thereof, and a specific example of nonionic surfactant is octyl phenoxy (polyethoxy) ethanol of Rohm & ~aas, sold under the trademark TRITON X-114 and an organic phosphate ester sold under the trademark GAEAC
RP-710 by General Analine and Film Corpoxation. Further examples of oxygenated solvents from tlle class of glycol ethers which may be used include methyl cellosolve, hexyl cellosolve, cellosolve solvent, methyl carbitol r carbitol solvent, butyl carbitol, hexyl carbitol, and the like. Other examples of ketones include methyl ethyl ketone, methyl isobutyl ketone, methyl isoamyl ketone, ethyl butyl ketone, isobutyl heptyl ketone, isophorone, diacetone alcohol, acetone, 4-methoxy-4-methyl-2-pentanone, and the like. Other examples of ethers include butyrolactone, diethyl carbitol and dibutyl carbitol, and others. Examples of esters include butyl lactate, butyl acetate, butyl carbitol acetate, carbitol aceta~e, butyl cellosolve acetate, cellosolve acetate, 2-ethyl hexyl acetate, amyl acetate, methyl cellosolve acetate, formates, and others.
Bxamples of alcohols include amyl alcohol, bu~yl alcohol, 5'~
furfurol alcohol, 2=butyne-1,4,diol, tetrahydrofurfurol alcohol, and others. Therefore, in accordance with the broader principles of this invention, oxygenated solvents from the above mentioned classes are suitable for use, depending upon the required solvating capacities of the oxygenated solvents in order to obtain the most desired biodegradability, least flammability and highest threshold limit values to meet or exceed health and safety standards. In accordance with the preferred principles of this invention, however, as mentioned above, there are specific examples which meet all of these criteria in the most preferred aspects of this invention~ In a generic aspect, the oxygenated solvent acilitates the low viscosity solvating character of the NMP and helps disperse it to solubilize or degrade the ink compositions. The NMP is also water active when needed. Thus, the combination of the NMP and the oxygenated solvent provide a coaction between organic co-solvents along with a unique water activity to provide a synergistic action in solvating or degrading ink compositions on screens for removal with water. Yet, it is imperative that the NMP concentrates be essentially non-aqueous during solvation or degradation o~ ink becau~e any significant water will destroy the efectiveness of NMP in its cleaning power as it is used in this invention. ~owever, the solvated or degraded ink must then be in a state for removal with a low-volume, pressurized stream of water.
In addition to the surfactants mentioned above, other nonionic, anionic, cationic and amphoteric surfactants may be used, as listed primarily in McCutcheon's Detergents and Emulsifiers, 1980 Edition, MC Publishing Company, Glenrock, New Jersey. The surfactants aid in the dispersion and degradation ~9~J~'7 !
of the inks for aqueous removal. Surfactants of the anionic type may be (1) of the group of saponified fatty acids or ~oaps, or (2) of saponified petroleum oil such as sodium salts or organic sulfonates or sulfates or (3) of saponified esters, alcohols or glycols, with the latter being well known as anionic synthetic surfactants. Examples of these anionic surfactants include the alkaryl sulfonates or amine salts thereof such as sulfonates of dodecyl benæene or diethanolamine salt of dodecyl benzene sulfonic acid. Most of these sulfonates contain many chemical species. The clas~ name given to most of them is ~alkylaryl sulfonate". Simply, this means that a paraffinic hydrocarbon is bonded to an aromatic or b~nzene nucleus and the aromatic portion has been sulfonated.
Examples of saponified fatty acids (C6-C2~) are the sodium or potassium salts of myristic, palmitic, s~earic, oleic or linol~ic acids or mi~tures thereof. Also in this class of anionic surfactants are organic phosphate esters including ~lk~li and alkaline earth metal salts of neutral phosphoric acid esters of oxylalkylated higher alkyl phenols or aliphatic O monohydric alcohols. Aerosol OT iS a dioctyl alkali metal sulosuccinate anionic surfactant made by Cyanamide. The nonionic surfactants suitable for use commonly have hydrophylic portions or side chains usually of the polyoxyalkylene type.
The oil soluble or dispersible part of the molecule is derived rom either fatty acids, alcohols, amides or amines. By suitable choice of starting materials and regulation of the length of the polyoxyalkylene chain, the surfactant parts of the nonionic detergents may be varied as is well known.
Suitable examples of no~ionic surfactants include alkylphenoxy , polyoxyethylene glycol, ~or example, ethylene oxide adduct of j .
*trade mark either octyl-, nonyl- or tridecyl- phenol and the like. These mentioned nonionic surfactants are usually prepared by the reaction of the alkyl phenol with ethylene oxlde. Commercial products are sold under the trademarks "Triton X-100 or X-114"
by Rohm and Haas Co. or "Tergitol" by Union Carbide and Carbon Corp. which are alkyl phenyl ethers of polyethylene glycol.
Other specific examples of nonionic surfactants include glyceryl monooleate, oleyl monisopropanolamide sorbitol di-oleate, alkylol amides prepared by reacting alkanolamides such as monoisopropanolamine, diethanolamine, or monobutanol ~m; ne with fatty acids such as oleic, pelargonic, lauric and the like. The cationic surfactants are also well developed and mainly include betaines and quaternary ammonium compounds.
Some specific examples of betaine~ include imidazoline hataines, aliphatic and carboxcyclic betaines, and betaines with hetero atoms in the hy~o~hobic chains such as dodecyloxypropyldimethyl aminoacetic acid. Typical of the quaternary ammonium compounds that may be mentioned are dime~hyl dicoco ammonium chloride, cetyl pyridinium acetate, methyl cetyl piperidinium proprionate, N,N dilauryl, N,N
dimethyl ammonium diethophosphate, and the like. Thu , i~ will be understood that o~her anionic~ cationic, amphoteric or nonionic surfactants may be employed in accordance with the principles of this inven~ion.
The amounts o ingredients vary over wide ranges, however, it is preferred to use a significant amoun~ of ~he N-methyl-2-pyrrolidone, iOe., about 30-85% by weiyhtO The oxygenated solvent is usually contained in an amount of about 15-35~ by weight. The remainder o the composition comprises a surfactant or a mix~ure of surfactants within the range of about 1 to about 5~ by weight. The N~ concentrates may also be supplemented with o~her organic solvents such as methylene chloride, trichloroethane, dimethyl sulfoxide and its deriva-tives t fluorocarbons and freons in amounts of about 10-30~ by weight where additional faster penetxating power may be desired for better ink solubili~ation. Such organic solvents are permitted which would not alter the essential cha~acteristics of the i~k cleaning compositions of this invention and may help to enhance activity penetration of the co-solvents in pene-trating, emulsifying and accelerating the degradation of the inks for subsequent removal.
In order to further illustrate the invention, refer-ence is made to the specific operating formulas detailed hereinafter and detailed methods of cleaning and reclaiming a printing screen.
EX~MPLE 1 75.72~ N-methyl-2-pyrrolidone 18.52~ Butyl Cellosolve 3.04% Cyclohexanone 2062% Octyl Phenoxy (Polyethoxy) Ethanol (TRITON-X-114) 0~10~ Organic Phosphate Ester (GAFAC RP-710) l2 ., 37.86~ N-methyl-2-pyrrolidone 9.26% Butyl Cellosolve 1.52~ Cyclohexanone 24.00~ Cellosolve Acetate 26.00~ Methylene Chloride 1.31~ Octyl Phenoxy (Polyethoxy) Ethanol (TRITON X114) 0.05% Oryanic Phosphate Ester (GAFAC RP-710) In the alternative to the specific ingredients of Example 2, 50% of Example 1 may be combined with ~6% of methy-lene chloride and 24~ cellosolve acetate. Examples 1 and 2 are preferxed forr~ s for the NMP cleaning concentrates because of their hiodegradability, reduced flammability and low TLV
values.
Before describing in detail the cleaning and re-cl~; ing of printing screens emloying the compositions of this invention, an understanding of certain underlying facts or terms is important. Flrst of all, the ink side o the printing screen is altPrnately called the squeegee side, the well side, or the front side, but or purposes of ~his description it will be called the ink side. The opposite side of the screen is called the back side, down side or prin~-contact side~ Again, for purposes of this description, it will be called the print~
contact side. The term "ink" will be ~he generic term for many I of the compositions that are employed in the practice of screen , printing including dyes or inks c~ ~-ly refPrred to as flexible enamels, synthetic enamels, fast-dry enamels, flexible lacquers, industrial lacquers, fla~ vinyl ink, vinyl half-tone . l3 :~4-~ 7 ink, fluorescent vinyl ink, gloss vinyl ink, satin vinyl ink, flock adhesive, transparent ink, metallic powders, acrylic ink, plastisol ink, mylar ink, ~extile ink, among many other types of inks. For general information on ink compositions, reference may ~e had to the catalog by KC Graphics, Inc.
1978-1979, copyright 1978 by KC Graphics, Inc. Reference may also be had to "Textile Screen Printing" by Albert Koslof~, Second Edition, International S~andard Book Number 0-911380-39-6 (1976). These sources will also serve as background information for the inks which may be cleaned with the inventive cleaning compositions. As developed above, the printing screen may be made from a number of materials and may have various mesh sizes. A mono-filament screen is a single strand of material for example of polyestex, nylon, stainless steel, silk, chrome-plated wire, or other things, which is woven into a specific number of squares per a ~ nsion~ i.eO, a 230 mesh means 230 open squares per square inch. A
multi-f;lAm~nt screen is comprised of a series of strands of similar materials jus~ mentioned, braided before weaving into the mesh measurement, i.e., 12xx150 mesh-would mean 12 interwoven strands subsequently woven into 150 open squares per square inch and, where th~P cross-over points of mesh occur, pigment can get into the strands and may become extremely hard to L~ ve. Thus, it may be determined by this description of I either the mono-filament or the multi-f;l~Qnt screens that the i requirements for complete removal of ink residue, for instance, may differ due to the construction of the screen. In particular, that last residue often referred to in the art as "ghost" ar "haze" would be more readily apparent in the ! multi-filament screens where pigment can get into ~he strands and becomes very hard to remove. There are a number of classes of emulsions which initially cover the print-contact side of the screen. For instance, a direct emulsion is a water-reducible substance which cures to a temporary, non-removable substànce when exposed to specific wavelengths light~ For instance, the art work can be placed over the fresh emulsion while it is still reactive to water and exposed to halide light, at which time the part o the emulsion not exposed to the light, because it is covered with the art, stays water-reactive. After a certain shooting or light exposure time, the art is Le...oved, the screen is then flushed with water and the part that has not been exposad to the light is flushed ou~, leaving the emulsion-void image area through which the ink flows through the screen for printing. The measure of difficulty of emulsion removal also relates ~o the number of coats which are put on the mesh, that is, dried and reapplied, and so forth, until you have between, for instance, 2 to about 5 coats of emulsion. Thus, the degree of difficulty in removing emulsion depends upon a number of factors including the number of coats, whethex it i5 strongly sensitized, the exposure time, type of light activation and chemical hardeners used after emulsion development, among other factors.
In view of the above b~ckground, the cleaning composition of Example 1 is a liquid non-aqueous solvent ! concentrate having a flash point of approxima~ely 203F ~95C) and it is designed to remove a large variety of inks and paints from screens. In another feature of the inven~ion, NMP
concentrate of Example 1 prepares or sensitizes many common ` emulsions for subsequent removal with a low-volume, high pressure water rinsing. It is fast, efficient, economical by . 15_ its capability of low-volume usage, biodegradable and does not carry the red label ~DOT flammable~ solvent designation. It is also safe on all screens and can be left on screens for extended periods prior to rinsing for cleaning. The composltion of Example 1 may be employed in a recirculating solvent system or in other portable systems. In the case of a recirculating solvent system, Example 1 concentrate is allowed to flow on the ink side of an inclined screen, whereupon it may be drained for approximately 5 minutes. Alternatively, the ink side of the screen may be sprayed in a light even pattern with a cohesive spray to prevent volatilization, followed by a dwell time of about 2-5 minutes. A pressurized unit is operated for example under about 30 to 100 psi (normally 40 psi) to provide a coherent stream of concentrate from a nozzle about 6" to 12"
away from the screen. Mists are avoided. In the case of either the recirculating solvent or spray treatment, the degraded inks are then easily removed by a light to high pressure, i.e., approximately 50 to 1000 psi, low-volume water rinse. Low-volume means 2 - ~ gallons per minute. A fan spray ~o has been found preferred to provide a balance of force and quantity. A suitable fan spray nozzle is the UniJet 65/01 manufactured by Spraying Systems Company of Wheaton, Illinois.
It is importan~, as developed above, that the screens on which the ink will be solubilized or degraded are free from water prior to cleaning. The presence of wa~er either in the NMP
concentrate or on the screen greatly destroys the efectiveness of the composition.
It has been found that the most preferred cleaning technique for achieving the advantages of the invention is the 3~ , method disclosed and claimed in said application Serial No.
"
*trade rnark by Cord and Valasek. In said application, the cleaning concen-trate is sprayed onto the ink side of the screen in a light even pattern and allowed to dwell or a short period of time, i.e., several minutes up to several hours, depending upon the factors involved in the cleaning system, composition of the inks, production timing, and so forth. During the dwell time, the liquid cleaning concentrate penetrates, emulsifies and solubilizes the inkO The ink stays on the screen, but its former ink character is destroyed. During the dwell time, the co-solvent actions of N-methyl-2-pyrrolidone and the oxygenated solvent are at work. Furthermore, the surfactant is pene-trating the ink composition for dispersion and to aid in later ink removal by water. The coaction of all three ingredients permits the solubili~ation or degradation of the ink permitting it to be dispersed for removal. The N-methyl-2-pyrrolidone provides water activity to the composition for removal with water, however, water must be under pressurized conditions such that the ink composition may be blown out; i.e., blown away from the screen. Thus, the composition is a delicate b~l~nce of ingredients whereby organic componen~s of the ink may ~e solubilized or degraded by both the N-methyl-2-pyrrolidone and oxygenated solvents. Fur~herr~rer even though water during the presence of the solubilization and degradation of the ink would i be detrimental to the activity of N-me~hyl-2~pyrrolidone, nevertheless, the degraded ink in the presence of the NMP and cosolvent is water-active and may be Lemo~ed from the screen with a pressurized fan of low-volume water rinse. In this connection it is preferred to employ a slicing fan or stream of water and sweeping it across the screen from the bottom upwards -in a manner such that the ink may be removed without redeposi-tion.
The composition of Example 2 above is employed in the same manner for cleaning as ~he liquid solvent concentrate of Example 1. However, the presence of methylene chloride tends to enhance the penetration o~ the entire composition and cellosolve acetate enhances the water solubility of ~.he composition. Other organic solvents which may be substituted for the methylene chloride include other chlorinated solvents like l,l,l-trichloroethane, dimethyl sulfoxide, its derivatives and fluorocarbons or Freons. In either case, the addition of such an organic ~olven~ which enhances penetration, may also tend to evaporate and, therefore, has a much shorter wet life or dwell time on the screen. For instance, whereas the composition of Claim 1 may be left on the screen surface for a number of hours, the composition of Example 2 is usually employed or several minutes, i.e., between 2-5 minutes for example. It is to be furthex understood that the ink solubilizer of Example 1 may be sequentially used in combination with the cleaning concentrate of Example 2. For instance, during the course of a cleaning operation, the ink may be solubilized with the Example 1 concentrate where an operation may require screens to be left from production for a period of time up to several hours prior to the rinse removal of the ink. In such a case~ the dwell tlme may be followed by a fresh degrading concentrate of Example 2 so that the residue i may be activated for subsequent removal with a low-volume, high pressure water rinse. Furthermore, the amounts of the mate rials sprayed onto the substrate vary but normally they are ,, ~., '.. ; /~
!;
t7 within the range of several ounces per several square feet, for example, 2-4 ounces per 6 foot square of screen.
Thus, preferably the method involves spraying of the concentrates of either of the Examples 1-2 onto a scraen. The spray is an economical and low volume usage ~ollowed by dwell time to solubilize or degrade the ink. Thereafter, a low-volume, high pressure water stream is directed at the sub strate, preferably a fan-spray is employed to slice through and help remove the destroyed ink composition. I the solubiliæed and degraded screen were simply dipped in water, the screen would not be effectively cleaned. There is a balance between the force and the quantity of the water which is employed which will be understood by the person of ordinary skill in the art in view of this description.
It has been o~served in connection wikh the method of cleaning the screens with a low area coverage spray, that a light mist may tend to settle on other rPm~; ni ng areas of degraded inks. It has been found that this problem can be alleviated or overcome by the addition of another component into the concèntrate. That component may b~ characterized as a hydrophobic additive and in particular it has been found that synthetic-water soluble oiIs sold under the tr~e~rk UCON are satisfactory. Depending upon the amount of wa~er mist or back-lash that is to be expected from the water rinse out, part of the surfactant package or liquid NMP concentrate may contain a water dispersible oil which functions ;nlti~lly as a water repellant to a light water spray or mist, but readily allows a low volume, pressurized stream of water to remove the ink ' compositions previously degraded and solubilized by the NMP
concentrate. Such water soluble oils are of the class of / q .
!
5'7 polyalkylene glycols, commonly known as UCON lubricants manufactured by Union Carbide Corporation, but other types and mixtures thereof could be used of differing water solubility.
A preferred high molecular weight one is UCON 50-HB5100.
Specific compounds include polyalkylene glycols, i.e., an oxirane polymer, CAS Registration No. 9038~95-3 or ethoxylated lanolin or exthoxylated castor oil. However, it is preferred that the oils of the types described herein do not leave a residue on the screen after an adequate water rinse.
When the printing screen is to be totally recl~im~, that is, cleaned and the emulsion removed completely, the process is as follows. When the process of printing is com-pleted, the operator cards or squeegees off any residual ink that is on the ink side of the screen as well as any ink from the print-contact side. From a very practical standpoint, inks are expensive and an attempt is made to return as much of the ink as possible. From a standpoint of cleaning, more excess ink requires more cleaning concentrate in order to remove the ink and reclaim the screen without haze or ghost residue.
After the screen is well carded, either before or after L~.. oval from the cleaning process begins. If the process is to be an i .d;ate reclaLm, either the concentrate of ~ le 1 or 2 may be used, generally spe~k;ng, depending on ink type. Either concen~rate is sprayed on the ink side of the screen and then moved to the reclaim area. In the process of immediate recla;m;ng, within about 5-10 minutes ater the application of either of the compositions of Examples 1 or 2, ;mmP~iate rec1a;r;ng should be commenced. After spraying with either concentrate, the image is flushed out from the print-con~ac~
side of the screen with high pressure water, as developed above, and this clears all o~ practically all of the ink. At the same -time, the entire surface of the emulsion is wetted with water to prepare it for the application O F a periodate-containing emulsion remover. I~ has been found that there is a synergistic action resulting rom use of the non-aqueous concentrate of ~xample 1 or 2 whose residue remains even after the water spray such that the emulsion is sensitized for faster removal. It is theorized, however, ~hat in -the immediate reclaim process, ~he emulsion is somehow softened or made more permeable for the treatment with a periodate-containing emulsion remover. A suitable example of an emulsion remover is exemplified by Example 3.
94.096% Water
2.880% Sodium Meta Periodate
3.000~ Monosodi~m Phosphate, Anhydrous 110 grams/1000 pounds batch of an Anionic Suxfactant Package of Equal ~mounts of GAFAC RP 710, ident~fied above and CALSOFT F-90 Isodium dodecylbenzene sulfonate) The above periodate con~lning remover is then sprayed onto the screen surface on the print side and i5 per-mitted to dwell there anywhere from about 15 ~econds to several minutes. This is generally an adequate time for degradation of the emulsion. Again a high pressure spray is employ~d to ciean the emulsion from the screen. As developed above, it is important that residual effects of ~he concentrate o~ Examples 1 or 2 af~er the water spray be utilized immediately by following with an application of the periodate-containing i i *trade rnark , .
!
~¢~J~
emulsion remover. It has been proven tha~ when more time elapses, for instance one-half hour, the emulsior. will be taken of wi~h greatex difficulty. Accordingly, there is a synergism between the residual effect of the cleaning compositions of this invention insofar as they coact with such periodate containing emulsion removers and provide the complete removal of the emulsion.
Finally, in the event that there is a residual ghost image as explained above, especially in connection with a multi-filament screen, a ghost or image remover may be employed. It is to be noted, however, that although there are at some time residual images, they are not necessarily a hindrance ~o further use of the screen and some screen printers are not particular where there is a tinge of residue as long as the mesh squares themselves are not blocked in the screen. If a ghost or haze remover is used, it is typically a caustic solution of oxygenated solvents. The reason for such usage is that they are water rinsable or soluble and leave no residue to cause emulsion problems la~er. In the ca~e of the ghost or haze removers of this type it is necessary to brush, roll or card them on as opposed to spraying because of the enhanced viscosity. A typical composition is as follows:
31.64% Cyclohexanone 19.40~ Cellosolve Acetate 38.83% Sodium Eydroxide 50%
9.61% DOWFAX 2Al Solu~ion Isodium Didodecylphenoxy-benzenedisulfonate 70%, sodium dodecylphenoxy-,~ benzenedisulfonate 30%) 0.01~ Brilliant Milling Red Dye i 0.51% GAFAC RP-710 (identified above) .~
*trade mark '7 For screens which will be delayed in processlng but which will be totally reclaimed, it is important to destroy the ink so that at some time thereater, that is in a matter of hours, the screen may be treated. For instance, the compo-sition o Example 1 is sprayed onto the ink side and, again, this is a cohesive spray of the type referred to above without mist so as to reduce volatilization. The screen is thus wet and ~he ink tends to stay wet or a period o~ time.. However, i there is a lapse of time before it goes to the screen shop or complete removal of the emulsion, there will be some tendency for drying and possibly some run-down on the print side o~ the screen. If this develops, then the print side of the screen may be resprayed with a composi~ion of Example 2 which acts to freshen up the solubilized residue after treat-ment with the composition of Example 1 to degrade the ink prior to being contacted with the water spray. At this point, upon respraying the print-contact side of the screen with a concen-trate of Example 2, and rinsing the emulsion is sensitized or conditioned for the subsequent action with the emulsion cleaner as mentioned above. Again, i~ a ghost or haze occurs, the ghost remover may be employed as set forth above.
One of the very significant aspec~s of the cleaning and reclaiming procedures is that no further-screen degreasing is required as is re~uired when products typically available in the pxior art have been used on screens to Le,.,ove the inks and emulsions. In the past, toluene, acetone, bleach, trisodium phosphate, and other solvents or cle~n;ng agents of the type indicated in the background of this inven~ion have been employed in order to el;m;nate screen oily residue at the end of processing. Accordingly, this invention offers a highly 1~ 23 f~,., advantageous system for ~he complete cleaning of inks and emulsions from printing screens in a manner heretofore unachieved.
In view o~ the above detailed description, printing screen cleaning and reclaiming compositions are provided with distinct advantages over the products now available. In addition, methods of employing the compositions of this inven-tion have been provided which are unique and opexate syner-gistically with other composi~ions in the process of cleaning and recl~;mlng screens. In view of the above de~ailed descrip-tion, it will be apparent to a person of ordinary skill in the art that deviations may be made from the specific examples and methods of operatiQn without departing from the spirit and scope of this invention.
What is cl~;m~d is:
!
~¢~J~
emulsion remover. It has been proven tha~ when more time elapses, for instance one-half hour, the emulsior. will be taken of wi~h greatex difficulty. Accordingly, there is a synergism between the residual effect of the cleaning compositions of this invention insofar as they coact with such periodate containing emulsion removers and provide the complete removal of the emulsion.
Finally, in the event that there is a residual ghost image as explained above, especially in connection with a multi-filament screen, a ghost or image remover may be employed. It is to be noted, however, that although there are at some time residual images, they are not necessarily a hindrance ~o further use of the screen and some screen printers are not particular where there is a tinge of residue as long as the mesh squares themselves are not blocked in the screen. If a ghost or haze remover is used, it is typically a caustic solution of oxygenated solvents. The reason for such usage is that they are water rinsable or soluble and leave no residue to cause emulsion problems la~er. In the ca~e of the ghost or haze removers of this type it is necessary to brush, roll or card them on as opposed to spraying because of the enhanced viscosity. A typical composition is as follows:
31.64% Cyclohexanone 19.40~ Cellosolve Acetate 38.83% Sodium Eydroxide 50%
9.61% DOWFAX 2Al Solu~ion Isodium Didodecylphenoxy-benzenedisulfonate 70%, sodium dodecylphenoxy-,~ benzenedisulfonate 30%) 0.01~ Brilliant Milling Red Dye i 0.51% GAFAC RP-710 (identified above) .~
*trade mark '7 For screens which will be delayed in processlng but which will be totally reclaimed, it is important to destroy the ink so that at some time thereater, that is in a matter of hours, the screen may be treated. For instance, the compo-sition o Example 1 is sprayed onto the ink side and, again, this is a cohesive spray of the type referred to above without mist so as to reduce volatilization. The screen is thus wet and ~he ink tends to stay wet or a period o~ time.. However, i there is a lapse of time before it goes to the screen shop or complete removal of the emulsion, there will be some tendency for drying and possibly some run-down on the print side o~ the screen. If this develops, then the print side of the screen may be resprayed with a composi~ion of Example 2 which acts to freshen up the solubilized residue after treat-ment with the composition of Example 1 to degrade the ink prior to being contacted with the water spray. At this point, upon respraying the print-contact side of the screen with a concen-trate of Example 2, and rinsing the emulsion is sensitized or conditioned for the subsequent action with the emulsion cleaner as mentioned above. Again, i~ a ghost or haze occurs, the ghost remover may be employed as set forth above.
One of the very significant aspec~s of the cleaning and reclaiming procedures is that no further-screen degreasing is required as is re~uired when products typically available in the pxior art have been used on screens to Le,.,ove the inks and emulsions. In the past, toluene, acetone, bleach, trisodium phosphate, and other solvents or cle~n;ng agents of the type indicated in the background of this inven~ion have been employed in order to el;m;nate screen oily residue at the end of processing. Accordingly, this invention offers a highly 1~ 23 f~,., advantageous system for ~he complete cleaning of inks and emulsions from printing screens in a manner heretofore unachieved.
In view o~ the above detailed description, printing screen cleaning and reclaiming compositions are provided with distinct advantages over the products now available. In addition, methods of employing the compositions of this inven-tion have been provided which are unique and opexate syner-gistically with other composi~ions in the process of cleaning and recl~;mlng screens. In view of the above de~ailed descrip-tion, it will be apparent to a person of ordinary skill in the art that deviations may be made from the specific examples and methods of operatiQn without departing from the spirit and scope of this invention.
What is cl~;m~d is:
Claims (29)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A printing screen ink cleaning composition for removing inks from images on said screen and for performance at room temperature consisting essentially of a non-aqueous biodegradable mixture of N-methyl-2-pyrrolidone, an oxygenated solvent and a surfactant.
2. The composition of Claim 1 wherein the composi-tion contains tetrahydrofurfuryl alcohol.
3. The composition of Claim 1 wherein the oxygenated solvent is selected from the group consisting of a butyl cellosolve, cellosolve acetate and cyclohexanone, and mixtures thereof.
4. The composition of Claim 1 wherein said surfactant is selected from the class consisting of nonionic, anionic and amphoteric surfactants, and mixtures thereof.
5. The composition of Claim 1 further comprising an organic solvent selected from the group consisting of methylene chloride, 1,1,1-trichloroethane, dimethylsulfoxide and trichlorotrifluoroethane, and mixtures thereof.
6. A printing screen ink cleaning composition for removing inks from images on said screen and for performance at room temperature consisting essentially of a non-aqueous biodegradable mixture of about 30 to 85%
N-methyl-2-pyrrolidone, about 10 to 35% of an oxygenated solvent and about 1-5% of a surfactant.
N-methyl-2-pyrrolidone, about 10 to 35% of an oxygenated solvent and about 1-5% of a surfactant.
7. The composition of Claim 6 wherein tetrahydrofurfuryl alcohol is substituted for an amount of said N-methyl-2-pyrrolidone.
8. The composition of Claim 6 wherein the oxygenated solvent is selected from the group consisting of a butyl cellosolve, cellosolve acetate and cylcohexanone, and mixtures thereof.
9. The composition of Claim 8 wherein said surfactant is selected from the class consisting of nonionic, anionic and amphoteric surfactants and mixtures thereof.
10. The composition of Claim 6 further comprising an organic solvent selected from the group consisting of methylene chloride, 1,1,1-trichloroethane, dimethylsulfoxide and trichlorotrifluoroethane, and mixtures thereof.
11. The composition of Claim 1 which additionally includes a water dispersible oil.
12. The composition of Claim 11 wherein the water dispersible oil is selected from the group consisting of polyalkylene glycol, ethoxylated lanolin and ethoxylated castor oil.
13. A method of cleaning a printing screen having a residue of ink on the surface thereof which comprises the steps of treating at room temperature the printing screen ink residue with a non-aqueous liquid composition consisting essentially of N-methyl-2-pyrrolidone, an oxygenated solvent and a surfactant, allowing the composition to dwell on the ink surface for a sufficient period of time to degrade the ink residue, and rinsing the degraded ink residue with a pressurized stream of water.
14. The method of Claim 13 comprising the additional step of mechanically agitating said composition on said screen under non-aqueous conditions before rinsing.
15. The method of Claim 13 wherein rinse water is applied as a fan spray.
16. The method of Claim 13 wherein water rinse is a pressurized low-volume water rinse.
17. The method of Claim 13 wherein the oxygenated solvent is selected from the group consisting of butyl cello-solve, cellosolve acetate and cyclohexanone, and mixtures thereof.
18. The method of Claim 17 wherein the dwell time of said ink surface is from about several minutes up to several hours.
19. The method of Claim 18 wherein after several hours dwell time the degraded ink is treated with a liquid concentrate of N-methyl-2-pyrrolidone, a oxygenated solvent, methylene chloride, and a surfactant prior to rinsing.
20. The method of Claim 13 wherein said liquid composition additionally includes a water dispersible oil.
21. The method of Claim 20 wherein said water dispersible oil is selected from the group consisting of polyalkylene glycol, ethoxylated lanolin and ethoxylated castor oil.
22. A method of cleaning and reclaiming a printing screen having a printed image of an emulsion and a residue of ink on the surface thereof which comprises the steps of treating at room temperature the printing screen ink residue with a non-aqueous liquid composition consisting essentially of N-methyl-2-pyrrolidone, an oxygenated solvent and a surfactant, allowing the composition to dwell on the ink surface for a sufficient period of time to degrade the ink residue, rinsing the degraded ink residue with a pressurized stream of water, contacting within a short time the water-rinsed screen with a periodate-containing emulsion remover, and flushing the resultant screen with a stream of pres-surized water to remove the emulsion image.
23. The method of Claim 22 wherein the periodate-containing emulsion remover is an aqueous solution of sodium meta periodate.
24. The method of Claim 23 wherein said periodate-containing emulsion remover additionally contains an anionic surfactant.
25. The method of Claim 22 wherein after the last water flush a caustic solution of oxygenated solvent is applied to the screen to remove ghost images.
26. The method of Claim 25 wherein the caustic solution of oxygenated solvent comprises a solution of sodium hydroxide, a oxygenated solvent from the group consisting of cyclohexanone, cellosolve acetate and mixtures thereof and one other surfactant.
27. The method of Claim 26 wherein methylene chloride is added to said caustic solution.
28. The method of Claim 26 wherein said other surfactant is an anionic surfactant.
29. The method of Claim 22 wherein, after said dwell time and prior to the first water rinse, spraying onto the resultant screen residue a composition comprising N-methyl-2-pyrrolidone, a oxygenated solvent, a surfactant, and an organic solvent from the group consisting of methylene chloride, 1,1,1-trichloroethane, dimethylsulfoxide and trichlorotrifluoroethane, and mixtures thereof.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US32778281A | 1981-12-07 | 1981-12-07 | |
| US327,782 | 1981-12-07 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1198957A true CA1198957A (en) | 1986-01-07 |
Family
ID=23278044
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000414431A Expired CA1198957A (en) | 1981-12-07 | 1982-10-28 | Printing screen cleaning and reclaiming compositions |
Country Status (3)
| Country | Link |
|---|---|
| JP (1) | JPH0249240B2 (en) |
| CA (1) | CA1198957A (en) |
| MX (1) | MX161242A (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2008003161A1 (en) * | 2006-07-05 | 2008-01-10 | Enviro Image Solutions Inc. | Method and composition for removing residual ink image from offset printing blanket |
| CN113293065A (en) * | 2021-05-15 | 2021-08-24 | 山东工业陶瓷研究设计院有限公司 | Pure organic terpineol slurry cleaning agent and preparation method thereof |
Families Citing this family (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH0718199Y2 (en) * | 1990-11-16 | 1995-04-26 | 岩崎通信機株式会社 | Cordless telephone handset |
| JPH04328938A (en) * | 1991-04-30 | 1992-11-17 | Matsushita Electric Ind Co Ltd | Portable telephone set container |
| JPH04126445U (en) * | 1991-05-08 | 1992-11-18 | 株式会社タナカ | portable radio phone with case |
| JP2873987B2 (en) * | 1992-01-16 | 1999-03-24 | 株式会社楽 | Water-soluble resin dissolving agent |
| JP3023231U (en) * | 1995-05-22 | 1996-04-16 | 株式会社エムアンドケイ・ヨコヤ | Cell phone storage case |
-
1982
- 1982-10-28 CA CA000414431A patent/CA1198957A/en not_active Expired
- 1982-12-06 JP JP21380982A patent/JPH0249240B2/en not_active Expired - Lifetime
- 1982-12-07 MX MX19547782A patent/MX161242A/en unknown
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2008003161A1 (en) * | 2006-07-05 | 2008-01-10 | Enviro Image Solutions Inc. | Method and composition for removing residual ink image from offset printing blanket |
| CN113293065A (en) * | 2021-05-15 | 2021-08-24 | 山东工业陶瓷研究设计院有限公司 | Pure organic terpineol slurry cleaning agent and preparation method thereof |
| CN113293065B (en) * | 2021-05-15 | 2023-09-01 | 山东工业陶瓷研究设计院有限公司 | Pure organic terpineol slurry cleaning agent and preparation method thereof |
Also Published As
| Publication number | Publication date |
|---|---|
| MX161242A (en) | 1990-08-24 |
| JPS58104795A (en) | 1983-06-22 |
| JPH0249240B2 (en) | 1990-10-29 |
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